Process for converting hydrocarbons



Jan. 4, 1938. F. E. FREY PROCESS FOR CONVERTING HYDROCARBONS Filed March 25, 1935 INVENTOR. FREDERICK E. FREY A TTORNEYS.

' ii Patent No; 2,002,394.

Patented Jar 1.4, 1938 v V A has PATENT ornca PROCESS FOR oo nx gmc Frederick E. Frey. Ma ne om. mm a Phillips Petroleum Company, eevllle,

Okla, a corporation otDelaware Application March 25, 1935, Serial No.- 1am This application is a continuation in part of appiicants co-pending application, Serial No.

731,920, filed June 22 1934 for a Process for converting hydrocarbons, patented May 21, 1935,

posed to heat simple olefins suchflas ethylene,--

propylene and butylene under pressure to obtain higher boiling products comprising essentially olefinic and cyclic polymers. Pressure accelerates the polymerization of olefins and under sufil- I ciently high pressurethe reaction takes place readily at temperatures too low to induce the 25 cracking of parafilns. The conversion oi lower paraflins, on the other hand, into products of higher molecular weight requires the use of a temperature sufiiciently high to efiect decomposition into simple .parafilns and olefins, 'and, when the pressure likewise is 'sufiiciently high, the

olefins formed then polymerize tolarger moleeules which undergo transformation into allcylic and aromatic hydrocarbons, as exposure to the high cracking temperature is continued; 7

A mixture of olefins and parafllns heated under high pressure will ordinarily exhibit the olefin polymerization, which may go to virtual'completion before substantial decomposition of the paramn takes place, olefins of high molecular weight 40 being chiefly formed.

I have discovered that, when the ratio of olefin to parafiinis very low, the olefin polymerization is discouraged by the low partial pressure, and the formation of'parafilns of high molecular weight may be eiiected. This reaction, I, have found, will take place under appropriate conditions, hereinafter set forth, to produce such parailinic products in high yield and withrelatiyely little concomitant formation of. less valuable bydrocarbons of lower molecular weight than the reactants. The reaction is particularly suited to the conversion 01'. gaseous para'iiins, propane and butane together with any of the gaseous olefins into volatile normally liquid hydrocarbons. An object oi. this invention is to provide a more (on. 190-10) I advantageous method for preparing other hydrocarbons from paraiiins and olefins in substantially the manner described, taking advantageoi the characteristics of the said reactions in order that they may be more readily conducted and controlled. The process consists in subjecting essentially saturated hydrocarbons, which may be propaneor butane, to a temperature at which decomposition will take place but very slowly, and under a pressure oi 1000 pounds-per square inch or more, adding thereto a small proportion of oleflns, not exceeding ten per cent by weight of the paraifins present, allowing the olefins to react, and adding from time to time as reaction proceeds additional small increments of olefins, or a hydrocarbon mixture containing olefins in a proportion exceeding that present in the reacting mixture, while maintaining the concentration of olefins in the said mixture at not more than ten per cent.

Hydrocarbons of higher molecular weight than carbons may be separated from unreacted hydrocarbons and scission products of low molecular weight by fractionation.

' The i'ormat'ion'oi high proportions of parafiins in the products and the development oi high yieldsofproducts heavier than the reactants from both parafllns and olefins in a mixture are favored by higher pressures which may be of 5000 pounds per square inch or more, limited only by the strength of the apparatus; At the higher pressures the ratio of olefin to paraflln in the reacting mixture, maintained by successive additions of olefin, should be maintained at a low value; at 4000 pounds pressure, for example, the

concentration of added olefin is best maintained V The reactionwili proceed without theme of catalysts, but in some cases they are beneficial.

Fig. 1 illustrates diagrammatically and partly in detail one form of apparatus for realizing the present invention, and,

Fig. 2 illustrates a modified form of the invention.

I have found that these reactions, being exothermic, may advantageously be conducted in the following manner. Referring to Figure 1 of the attached drawing, predominately saturated hydrocarbons are fed to the system through the line I. After being mixed with recycle stock from line H, and small quantities of olefins, if desired, from Ine II, the mixture is fed to the coil 2 in the heater 3. Here it is heated slightly, but generally to a degree insuilicient to cause an appreciable reaction. It is then passed through the line 4 into the heat exchanger I, which may suitably consist as shown of a shell adapted torwithstand high pressures, within which is positioned an elongated conduit, around which a stream of hydrocarbon is directed by suitably arranged banies, such as the one shown at 2 l, and may be passed generally concurrent to and in indirect heat exchange relation to the elongated conduit, as is shown in Fig. 1. To various points in the conduit olefins are fed through the pipe H and reaction takes place in the said conduit with evolution of heat. Reaction products from line I may be allowed to flow through line I1 and valve to the passageways surrounding the conduit to impart heat to the unreacted incoming hydrocarbons and'extract heat resulting from the reaction, being discharged through line I! to the fractionater 8. The hydrocarbons leaving the heat exchanger 5 by way of the line I will contain, due to the conversion which has taken place therein, a considerable amount of heat units which. would ordinarily be lost if it were not for the fact that provision is made to circulate a portion thereof back'into the heat exchanger. To accomplish this, part of the converted hydrocarbons leaving through pipe I is allowed to fiow through the valve l8 and pipe I! to the top part of the heat exchanger through which it flows in-heat exchange relation with the hydrocarbons in the, coils and thereby maintains them at conversion conditions. Valve 20 regulates the volume of hydrocarbons passed in this way. By a suitable arrangement of the conduit, the shell may be maintained relatively cool. These olefins fed through the pipe ll may, of course, be diluted with paraifins or other hydrocarbons, provided that the olefin concentration is higher than that to be maintained within the reacting mixture in the heat exchanger 5. Such dilution will, in fact, be desirable, since it will prevent excessive polymerization of olefins prior to their dispersal throughout the flowing stream passing through the heat exchanger 5, and any excess heat' of reaction will also be avoided. From the heat exchanger, the reacted hydrocarbons may pass through the line I, valve 20 and line I! to the fractionator 8, when hydrocarbons of higher molecular weight than the reactants will be separated from the products and withdrawn through the cooler 22 and the line l6. The overhead product from the fractionator will go through the line 9 to the fractionator l0, where light gases will be separated and withdrawn through the line l2 while recycle stock containing chiefly unchanged reactants is passed through line I I back to the heater 2. Olefins will be introduced at It, and will be pumped through lines I4 and I5 substantially as shown.

The heat exchanger 5 may obviously be varied in design provided the essential conditions for the reaction as set forth in the foregoing are maintained. For example a series of tubes with heat exchange between tubes by means of iron laminae, or molten metal, may be employed to advantage.

In some cases, particularly where olefins in concentrated form are being injected, some means for increasing turbulence at the point of injection may be desirable, in .order that simple polymerization of the olefins prior to their mixture with the flowing stream may be minimized.

A further modification of the process is shown in Figure 2, wherein A represents a heater, B a heat exchanger, C and D points for the admission and withdrawal of hydrocarbon and E a pump. Predominantly saturated hydrocarbons are circulated by pump I through the heater A and the exchanger B, olefin-containing hydrocarbons being admitted from time to time, or continuously, through the line C. Hydrocarbons may be withdrawn either continuously or after olefin addition, as desired, through the line D for separation and other processing or for reacting with additional olefin. 'Ihe essential conditions may be met by maintaining a body of saturated hydrocarbons in a state of turbulence at reaction temperature and pressure while adding olefin-containing hydrocarbons at such a rate that the concentration of added olefin is less than ten per cent of the reaction mixture.

While I have described my process .as used to produce normally liquid hydrocarbons from normally gaseous hydrocarbons, itvis evident that its utility is not limited to such use. It may be used to convert any straight chain, or moderately branched paraiiinic, aromatic or naphthenic hydrocarbon into a mixture of hydrocarbons of more complex structure, thereby efiecting significant changes in its properties, such as antiknock value or melting point. Saturated hydro-- carbons of high molecular weight as well as low may be used, including heavypetroleum fractions.

What I claim and desire to secure by letters Patent is:

1. A process for producing hydrocarbon mixtures containing at least 50% of saturated hydrocarbons, comprising heating a stream of predominantly saturated hydrocarbons to a reaction temperature under pressures in excess of 1000 pounds per square inch, adding olefin containing hydrocarbons to the said stream at a plurality of points, thesaid points being so spaced as to allow appreciable reaction to take place before the subsequent addition of further olefins, and so arranged that indirect generally concurrent heat exchange takes place between the said reacting stream and a representative portion of the stream after reaction takes place following the last olefin addition, and maintaining the content of unreacted added olefins in the mixture at not more than 10% by weight of the hydrocarbons present therein.

2. An improved process for the production of direct heat exchange with the aforesaid reacted hydrocarbons, olefin containing hydrocarbons at a plurality oi points, the points being so spaced of olefin containing hydrocarbons so that the content of unreacted added olefins in the mixture does not exceed 10 per cent by weight of the hydrocarbons present, passing a representative portion of the still hot reacted hydrocarbons in generally concurrent indirect" heat exchange relationship with the aforementioned heated stream of hydrocarbons and finally separating normally.

liquid predominantly ,paramnic' hydrocarbons from the reacted mixture.

3. The process for producing predominantly paraifinic hydrocarbons or higher molecular weight from parafilns and olefins of lower molecular weight which comprises the steps of maintaining a predominantly parafiinic hydrocarbon mixture in continuous circulation in an endlesscirculatory cycle which contains a reaction zone and a zone of hydrocarbon introduction, adding olefin containing hydrocarbons at the zone of hydrocarbon introduction thereby producing a hydrocarbon mixture such that the concentration of unreacted added olefin does not exceed ten per cent byweight of the total hydrocarbon mixture,

, passing the mixture to the reaction zone wherein a reaction takes place and maintaining therein a reaction temperature and a pressure in excess of 1,000 pounds per square inch, passing the reacted mixture back to the zone of hydrocarbon introduction thus completing the endless circulatory cycle, withdrawingat some point in the cycle a portion of the mixture and separating therefrom predominantly parafilnic hydrocarbons of higher molecular weight.

4. In a process for producing higher boiling hydrocarbon mixtures containing at least 50per cent by weightot parafiinic hydrocarbons from lower boiling hydrocarbons, the steps which comprise heating a stream 01 predominantly parafiinic hydrocarbons to a preheat temperature and then to a reaction temperature by heat exchange with hotter reaction products under a pressure inexcess of 1,000 pounds per square inch, adding olefin containing hydrocarbons to the said stream at a plurality of points, the said points being so spaced flow of the said reacting stream being so directed that generally concurrent indirect heat exchange takes place between the said reacting stream and a'representative portion of the-stream aiter reaction takes place following the last addition of olefin, maintaining the content of unreacted added olefins in the reacting stream at not more than '10 per cent by weight of the hydrocarbons present therein, and separating from the totalreacted stream higher boiling hydrocarbons produced.

5. In a process for continuously producing predominantlyzparafllnic hydrocarbons of high molecular weight from paraffins and oleflns of lower molecular weight, the steps which comprise maintaining a stream of predominantly parafiinic hydrocarbons in independent cyclic circulation through areaction zone wherein a reaction temperature and a pressure in excess of 1,000 pounds per square inch are maintained and wherein a reaction takes place consuming parafiin and added olefin hydrocarbons; introducing into said.

stream an olefin containinghydrocarbon mixture such that the concentration of added unreacted olefins do not exceed 10 per cent by weight 01 the total. mixture local to the point of introduction, withdrawing iromthe said stream a portion thereof and separating therefrom predominantly parafllnlc hydrocarbons or higher molecular weight.

6-. A process forcontinuously producing predominantly paraifinic hydrocarbon mixtures of high molecular weight from parafiin and olefin hydrocarbons of lower molecular weight, which comprises maintaining a stream composed predominantly oi 'parafiin hydrocarbons in independent cyclic circulation through a heating and reaction zone, wherein a reaction temperature and a pressure in excess of 1,000 pounds per square inch are maintained and wherein reaction takes place consuming said parafiin hydrocarbons and added unreacted olefin hydrocarbons, and through a heat exchanger such that indirect heat exchange takes place between hydrocarbons leaving said heating and reaction zone and hydrocarbons entering said heatlng and reaction zone, introducing olefin hydrocarbons into said stream in such amount that the added unreacted olefins do not exceed 10 per cent by weight of the total mixtureat the point of said olefin introduction, withdrawing from said stream a portion thereof and separating therefrom a hydrocarbon mixture so produced .of higher molecular weight and predominantly paramnic.

FREDERICK E. FREY. 

